Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.69	4.658%	$105.3801	$105.38	$105.40	$105.40
Purchase #2	$126.55	3.690%	$131.2197	$131.22	$131.20	$131.20
Purchase #3	$142.62	9.513%	$156.1874	$156.19	$156.20	$156.20
Purchase #4	$195.57	4.349%	$204.0753	$204.08	$204.10	$204.10
Purchase #5	$238.44	9.583%	$261.2897	$261.29	$261.30	$261.30
Purchase #6	$149.56	12.429%	$168.1488	$168.15	$168.15	$168.10
Purchase #7	$117.64	10.801%	$130.3463	$130.35	$130.35	$130.30
7 purchase totals =	$1,071.07		$1,156.6473	$1,156.66	$1,156.70	$1,156.60